Merge pull request #4 from erelson/fixes4pololu

Comment fix; uartNTxSend -> uartNTxAvailable
gpio.h: Fixed a typo.
Merge branch 'master' of github.com:pololu/wixel-sdk
Added the example_pwm app.
example_pwm app: The word 'alternate' in the comments is not actually correct so I got rid of it.
example_pwm app: Fixed the description of the PWM frequency.
example_pwm app: Changed it to use 11.7 kHz by default because we sell motor drivers that do not support 23.4 kHz.  Made it easy to switch to 23.4 kHz is desired.
example_pwm app:  Call it 'Timer 1' instead of 'the Timer 1'.
example_pwm app: Fixed the line that was configuring the location of Timer 1.  It should configure Timer 3 instead.
example_pwm app: It is not so easy to use Timer 4; fixed the comments.
added: serial_ascii_binary app
serial_ascii_binary app: Moved the big comment to the top.
serial_ascii_binary app: A few changes to the comments to make it more clear which interface is for ASCII and which is for binary for someone who just wants the information fast.  Also fixed the conversion to lower case so it is only done in the correct place.  Also got rid of unused static variables.
serial_ascii_binary app: Improved some other comments.
serial_ascii_binary app: Fixed one of my comments.
Typo fix